It is known that in construction, for example, of individual dwellings or buildings, and in all masonry work in general, the bonds between the construction elements, such as plates, panels, squares, etc., are made with mortar for joints, the thickness of these usually being between 1 and 2 cm.
When these construction elements consists, for example, of concrete with a base of natural aggregate whose useful thermal conductivity coefficients ".lambda.u" are between 1.15 and 1.75 W/m.degree.C. (watts per meter and per degree C.), the influence of mortar joints with a natural sand base is not appreciable from the heat loss viewpoint, because the coefficient .lambda.u of the mortar is on the order of 1.15 W/m.degree.C.
On the other hand, if light concrete blocks are used whose thermal conductivity is clearly lower (.lambda.u between 0.2 and 0.5 W/m.degree.C.), the joints of normal mortar make the wall heterogeneous and are the origin of considerable heat bridges and heat losses.
The space occupied by the joints in the construction is far from being negligible. For example, when blocks 50.times.20.times.27.5 (cm) are used for making finished walls 30 cm thick, joints of 1 cm or 2 cm represent respectively 6.4% or 12.88% of the total wall surface. Further, heat losses due to the joints are not proportional to the surface; thus it has been determined that for a wall made up of light blocks erected with normal mortar representing about 10% of the total surface, the heat loss due to the joints is on the order of 40% of the total caloric loss.
A technical problem therefore arises at the level of the choice of mortar suitable for joints with good heat insulation and suited to the construction element used.